Process of making ammonium nitrate and other products.



F. S. WASHBURN. PROCESS OF MAKING AMMONIUM NITRATE AND OTHER PRODUCTS.

. APPLICATION HLEDMAY 6 1916. 1,217,247

Patented Feb. 27, 1917.

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UNITED STATES PATENT onmicn.

FRANK S. WASHBURN, OF NEW YORK, N. Y.

' PROCESS or MAKING AMMONIUM nrrnn'rn AND OTHER PRODUCTS.

1,217,247. Original application filed February 7, 1916,

provements in Processes of Making Am-' monium Nitrate and, otherProducts; and I to which it appertains invention consists in do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to make and usethe same.

This invention relates to a process of treating ammonia in such a manneras to produce a highly concentrated nitric acid simultaneously withother useful ammonia salts, and has for its object, to provide a meansand a method that will obviate the inherent difiiculties in theprocesses heretofore proposed, while enabling one to operate moreefliciently and economically.

With these and other objects in view the the novel combinations of stepsconstituting the process as will be more fully hereinafter disclosed andparticularly pointed outin the claims.

This application is a division of my prior application Serial Number 76647 filed Feb} ruary 7, 1916 and entitled Process of and apparatus formaking nitric acid and other products.

In the well known processes of oxidizing;

ammonia it has long been recognized that when subjecting the ablecatalyzer, a simultaneous the ammonia to nitrose gases and a decomposition of these n'trose gases to nitrogen gas takes place. It=is,therefore, well recognized that one must so control reactions that thevelocity of the oxidation reaction'is very materially greater than'thevelocity of the decomposition reaction, for other-wise, one willdecompose too much of the nitrose gases to enable a commercialpracticable process to result.

In one of the prior processes the relative velocities of these two thesize of the catalyzing mass-and the ve locity of the gases passingthrough it, that all the ammonia is either oxidized or decomposed, andnone gets past in the form of free ammonia. But the control of the ve-Speciflcation of Letters Patent.

Serial No. 76,647. Divided and this application 1916. Serial No.95,897.

v ammonia and oxygen contalnmg mixture to the influence of asultoxidation of,

. designing these simultaneous simultaneously occur- I ring reactionsare controlled by so adjusting Patented Feb. 27,191'7. med ma 6,

locity of such gases, particularly ammonia, is very complicated anddifiicult, for it is influenced to a considerable extent by the relativequantities of ammonia and oxygen contained in the mixture, as Well as bythe actual rate at which the gas passes the catalyzer. In practice it isnot only difficult to maintain the desired uniform mixture containingthe right proportions ofammonia and oxygen but even with a carefullydesigned catalyzer, it is" almost impossible to pass every portion ofthis mixture at exactly the right rate uniformly, over every portion ofthe catalyzer, so that no'free ammonia escapes through without sufieringa decomposition or an oxidation.

Accordingly this said the average, as been prior process, on forced tooperate case other difiiculties will result as will be now explained. I

That is to say, technical difficulties in and operating the oxidizingapparatus prohibit the employment of such a speed in the mixture passingthe catalyzer as be passed at such a rate over or through the catalyzerthat free amducts of the reac;

in order will produce a very large excess offree-ams monia on the exitside of the said catalyzer; but it is, yet commercially possible toemloy such a speed through the catalyzer as will permit the productionof large quantities of nitrose gases, and some free ammonia, so thatsaid nitrose gases may be converted into nitric acid and said freeammonia may combine with said acid to form ammonium nitrate, as willmore fully appear below. In other words, should too much free ammoniafbethus converted into am monium nitrate it will tend to condense in acidin the usual and the colder portions of the apparatus, and clog them upso it is only by operating very skilfully in such cases that ticallycarry out the direct production of ammonium nitrate in this way.

It is, however, very convenient to permit say 5% to 15% of the ammoniafed to the catalyzer to pass through undecomposed, and it is with suchrelative smaller quantities of free ammonia, that I prefer to operate.

In carrying out this invention I prefer to pass this free ammonia alongwith the nitrose gases through a suitable cooler and into an oxidationtower, when with a properly designed apparatus, a very large proportionof that passing the catalyzer can be kept from decomposition, and passedinto the oxidation and absorption towers as free ammonia, where itcombines with the nitric and nitrous acids formed and finally appears asammonium nitrate dissolved with dilute nitric acid.

This dilute nitric acid is next concentrated by a suitable means. But aconcentration by means of any of the well known sulfuric acid processes,converts this ammonium nitrate into ammonium sulfate and nitric acid,which acid can be recovered as such; and when the sulfate hasaccumulated to a suitable concentration, it of itself, will precipitateout, and is recovered from the sulfuric well known manner. As analternative method I may so operate that I permit free ammonia to passthe catalyzer and form ammonium nitrate dis solved in nitric acid asabove described and I then saturate the excess of nitric acid withammonia from an outside'source so as to produce from my oxidationapparatus ammonium nitrate as itssole product. This solution can bereadily evaporated and crystallized, thus producing a dry ammoniumnitrate which can be marketed as such or employed in many industries.

In case I do not desire to market the ammonium nitrate produced asabove, I can treat the dry ammonium nitrate with a suitableconcentration of sulfuric acid and convert all of it into ammoniumsulfate and highly concentrated nitric acid, which two products alsofind a ready market.

I have further found, when the velocity of my gas current, containing.ammonia and oxygen, is increased, through, or over the catalyzer, tosuch a point that ammonia passes the catalyzer undecomposed, I am reallyobtaining a'maximum velocity of the ammonia oxidation reaction, and aminimum velocity of thnitrose gas decomposition, referred to above, soin such case,I obtain a very much higher'eificiency of oxidation of theammonia composition of either the ammonia or of the nitrose gases, thanis the case where I so limit the velocity of these gasesthrough one canprac-- with considerably less de or over the catalyzer to such an extentthat no ammonia appears in the products of the oxidation, as such.

It therefore follows that quantity of free ammonia that passes thecatalyzer, I am enabled to judge the real efliciency of the chemicalreaction that is going on. In fact, it is a comparatively simple matterto oxidize ammonia by this system at an efficiency far above 90% ifproper account is taken of the undecomposed ammonia passing thecatalyzer.

In carrying out the process, I prefer to use a mixture of predeterminedproportions of ammonia and oxygen, of ammonia air and oxygen or ofammonia and air, and to precool the same all in a manner similar to thatdisclosed in the copending application of Walter S. Landis, filedFebruary 15, 1915, Serial N o. 9595, and entitled Method of andapparatus for oxidizing ammonia.

In order that the invention may be the more clearly understood,reference is had to the accompanying drawing forming a part of thisspecification, in which the figure is a diagrammatic partiallysectional, partially elevational view of an apparatus suitable forcarrying out-the process.

Referring to the said drawing, 1 indicates any suitable conduit forsupplying the ammonia mixture to be oxidized, connection leading fromsaid conduit to the oxidizing chamber 3. Located in the chamber 3 is anysuitable form of cooler 4 adapted to cool the gaseous mixture beforereaching the catalyzer, 5, or to screen the oncomby observing the 2 avalved ing stream of ammonia from the heat radiated from said catalyzer.The catalyzer may be of any suitable material, but I prefer-iridium freeplatinum of a uniform cross section in order that it may be uniformlyheated by an electric current.

After the gaseous mixture passes the catalyzer 5, it will be found tocontain the oxids of nitrogen mixed with ammonia, water vapor and freenitrogen, if air was originally employed, and this mixture passesthrough the valved connections 6 to the conduit 7, thence preferablythrough a cooler 8, having a coil 9 ,and a supply 10 for a coolingmedium.

From the cooler 8, the said mixture is contion tower 11 which may besupplied with water through the pipe 12, when the nitrose gases and freeammonia are readily taken up. A reaction now occurs by which there isformed a solution of nitric acid and ammonium nitrate which may bedrawn. off through the valved pipe 13 into the tank 14:,

solution may be veniently passed through a suitable absorpthe valvedconration of its nitrogen containing constituents, it may be repeatedlycirculated through the tower 11 by means of the pump 18, pipe 19, tank20 and valved connection 21, the unabsorbed gases in all cases escapingfrom tower 11 through the pipe 22. If the tower 11 is so designed as toabsorb all the ammonia and nitrose gases delivered to it, then the othergases contained in the mixture may be led to waste through said pipe 22.But in those cases, where it is less expensive to run..the said nitrogencontaining gases through a plurality of towers, in order to absorb allthe combined nitrogen the said pipe 22 is led to one towers such as 25,from which gases escape through the pipe 26.

The tower 25 may be conveniently supplied with water through the pipe27, and connected with the tank 20, through the pipe 28. The solution ofnitric acid and ammonium nitrate formed in said tower 25 may beconveniently delivered through the connection 30 to the tank 31, fromwhich it may be drawn off by means of the valved connections 32, 15 and16 when desired, or when said solution is found to be too weak fordrawing oif it may be repeatedly circulated back throughsaid tower 25,by means of the pump 18, pipe 19, tank 20 and connection 28. A valvedpipe 35 permits the contents of the tank 31 to be emptied at will intothe tank 14.

When it is desired to convert all the nitric acid into ammonium nitratefree ammonia may be led to the tower 11 through the valved pipe 40.

It is obvious that those skilled in the art may vary the" details ofboth the process and apparatus without spirit of'the invention, andtherefore, I do not wish to be limited to the above disclosure except asmay be required by the claims.

WhatI claim is 1. The process of producing ammonium nitrate, whichconsists in subjecting a mixture of ammonia and oxygen containing gasesto the actionof a catalyzer and at such a rate as to cause nitrous gasesand free ammonia to appear in the products of the reaction; producing asolution of nitric acid the waste or more additional departing .from theand ammonium nitrate from said products; and adding free ammonia to saidsolution to convert said nitric acid into ammonium nitrate,substantially as described.

2. The process of producing a concentrated nitric acid, which consistsin subjecting a mixture of ammonia and oxygen containing gases to theaction-of a catalyzer and at such a rate as to cause nitrose gases andfree ammonia to appear in the products of the reaction; producing asolution of nitric acid and ammonium nitrate from said products; addingfree ammonia to said solution to convert said nitric acid into ammoniumnitrate; suitably recovering said nitrate; and treating said nitrate toform a concentrated nitric acid, substantially as described.

3. The process of producing ammonium nitrate, which consists insubjecting a mixture of ammonia and oxygen containing gases to theaction of a catalyzer and at such a rate as to cause nitrous gases andnot exceeding 20% of free ammonia to appear in the products of thereaction; producing a solution of nitric acid and ammonium nitrate fromsald products; and adding free ammonia to said solution to. convert saidnitric acid into ammonium nitrate, substantially as described.

4. The process of producing a concentrated nitric acid and whichconsists in subjecting a-mixture of ammonia and oxygen containing gasesto the action of a catalyzer and at such a rate as to cause nitrosegases and not exceeding 20% of free ammonia to appear in the products ofthe reaction; producing a solution of nitriq acid and ammonium nitratefrom said products; adding free ammonia from an outside source to saidsolution to convert all of said nitric acid into ammonium nitrate;suitably recovering said nitrate; and treating said nitrate to form aconcentrated nitric acid, substantially as described.

In testimony whereof I afiix my signature in presence of two witnesses.

BRUNN DELANY, G. M. SoHu'RMAn.

